1. Field of the Invention
The present invention relates to an image capture device having a function of removing the noise of an image which has been shot.
2. Description of the Related Art
Conventionally, image capture devices having a function of removing the noise which occurs in an image sensor or the like are known. For example, an image capture device which is described in Japanese Laid-Open Patent Publication No. 11-41491 suppresses random noise through a low-pass filtering process using a two-dimensional filter.
In a low-pass filtering process using a two-dimensional filter, a pixel to be processed and a plurality of pixels (“neighboring pixels”) positioned in the neighborhood of that pixel are utilized to determine a pixel value for the pixel to be processed. Specifically, by utilizing the pixel value of the pixel to be processed and the pixel values of the neighboring pixels, presence or absence of correlation between the pixel to be processed and each neighboring pixel is determined. Then, an arithmetic mean value of the pixel value of the pixel to be processed and the pixel values of those neighboring pixels which have been determined as being correlated is calculated, and this value is used as the pixel value of the pixel to be processed.
The noise suppression effect of a two-dimensional filtering process depends on the range of pixels utilized for the calculation of an arithmetic mean value. In order to obtain a large effect, it is necessary to select neighboring pixels from a wide range over the image, so as to be subjected to correlation determination. Especially in order to suppress low-frequency noise, it is necessary to select a plurality of neighboring pixels from a wide range, and their pixel values must be added. However, increasing the range of neighboring pixels leads to an increase in the capacity of the memory for storing the pixel values of the neighboring pixels, as well as an increase in the scale of circuitry need for correlation detection and addition/subtraction. This invites an increased cost of the image capture device, and hinders downsizing.